Railway track circuit apparatus



` mvENToR Jiyrezzsezz. A

HIS ATTORNEY J J 51! 1 v A N mm. N TQM. T .jllm ItTV 211x E.. u

A. J. SORENSEN l RAILWAY TRACK CIRCUIT APPARATUS Filed Sept. 22, 1959 .m ww Sw mm NSN QN EN: mw 5S: 28S Nm. lp. ma UQIN n QT wm mm www w .N bm. N QN w Nov. l2, 1940.

Patented Nov. 12, 1940 UNITED STATES PAE OFFCE 2,221,7 26 RAILWAY TRACK CIRCUIT APPARATUS Applicationseptember 22, i939, serial No. 296,117

7 Claims.

My invention relates to railway track circuit apparatus, and particularly toy apparatus for track circuits using coded direct current.

Railway track circuits have been proposed which use time spaced impulses of direct current with the individual impulses of relatively high peak voltage and short duration as compared with the duration between successive impulses.

The high peak voltage serves as an aid to the shunting sensitivity of the track circuit and the short duration serves to limit the output of the current source to a relatively low energy level. In such track circuits code following track relays are provided for controlling the signaling circuits. It has been found that when adverse train shunting conditions prevail due to rusty rail surfaces, light-weight high speed trains and other operating conditions, a few impulses of current of sucient magnitude to operate the track relay may reach a relay now and then past the poor train shunt with the result that a proceed signal indication may be falsely established for an interval.

Accordingly, a feature of my invention is the provision of novel and improved apparatus for track circuits of the type here contemplated wherewith the display of a proceed signal indication is not effected until the track relay has responded to several successive impulses of the track circuit current. Another feature of my invention is the provision of novel and improved apparatus for track circuits of the type here involved which is selectively responsive to both the polarity and magnitude of the voltage of such track circuit current impulses. Other features and advantages of my invention will appear as the specification progresses.

I shall describe one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawing, Fig. 1 is a diagrammatic view showing a preferred form of apparatus embodying my invention. Figs. 2 and 3 are diagrams illustrating operating characteristics of the apparatus of Fig. 1.

Referring to Fig. l, the reference characters la and lb designate the track rails of a stretch of railway track which rails are formed by the usual insulated rail joints 2 into consecutive track sections of which sections only the one full section W-X and the adjoining ends of the two adjacent sections are shown for the sake of simplicity. Each track section is provided with a track circuit comprising a lsource of coded direct current connected across the rails at one end of the section and a code following relay connected with the rails at the other end of the section.

The source of coded direct current for the track circuit of section W-X comprises a battery 5, a code transmitter CT and a track transformer XT. The code transmitter CT may take the form of any one of the several well-known structures for such devices and it is sufficient to point out that as long as the operating winding (t of code transmitter CT is supplied with current from any convenient source (not shown) a contact member 'l is operated at a preselected code rate, such as, for example, operation cycles per minute.

The contact member l alternately engages a normal Contact 8 and a reverse contact 9 each operation cycle. The interval required for movement of the contact member 'l between the two contacts 8 and Sis short and only a small portion of the operation cycle, and the interval contact member l engages either contact 8 or 9 is one-half the operation cycle interval less the interval required for contact member l to move between its two positions. The contact member l and the associated contacts B and 9 are used to controlthe supplyvof current from battery 5 to the `track transformer XT. When contact member l engages normal contact 3, current is supplied from battery t to the left-hand half portion of primary winding It of transformer XT and when contact member l engages reverse contact 9, current is supplied to the right-hand half portion of primary winding Mi as will be apparent by an inspection of Fig. 1. A condenser i3 may Vbe connected across the primary winding lll to improve the operation.

A secondary winding H of transformer XT is connected across the rails according to traflic conditions in .advance of section W-X. A mid terminal of secondary winding H of transformer XT is connected with rail Ib over wire i2. The

rail la is connected with either the right-hand or the left-hand terminal of secondary winding H according to different trafc conditions yin advance of the section. To be explicit, the lefthand terminal of. secondary winding il is connected with rail la over wire i3, a back contact lll of a relay XRE to be later described, and wire l5; while the right-hand terminal of secondary y Winding l I is connected with rail la over wire I6, front contact ll of relay XRI and wire l5.

It is to be seen, therefore, that each time either contact l-S or "5 9 of code transmitter CT is closed direct current ows in either the left-hand ondary Winding I I when the magnetic energy decays. Consequently, when front contact I7 of relay XRI is closed connecting the right-hand portion of secondary winding I I with the rails of section W-X, a high voltage current impulse is supplied to the rails each time contact 1 8 or '1 -9 is opened, and a low voltage current impulse is supplied to the rails each time either contact 1 8 or 1 9 is closed. The parts are so arranged that when relay XRI is picked up closing Yfront contact I1 the high voltage current impulses supplied to the track rails of section W-X are of positive polarity and the low voltage current impulses are of negative polarity. This characteristic of the current impulses is illustrated by the graphs of Fig.l 2. When relay XR! is released closing back contact I4 to connect the left-hand portion of secondary winding II across the rails of section W-X, the high voltage current impulses are of negative polarity and the low voltage current impulses are of positive polarity as illustrated by the graphs in Fig. 3. Furthermore, as illustrated in Figs. 2 and 3 each individual high voltage current impulse is of short duration as compared to the duration between such successive impulses. Also, it is to be observed that a high voltage current impulse is followed immediately by the next succeeding low voltage current impulse because the time required by contact member 1 to move from engagement with one contact 8 or 9 into engagement with the other contact is short.

It is to be seen, therefore, that when trafc conditions in advance of section W'-X are such as to cause relay XRI to be picked up in a manner to later appear, code impulses of direct current of the pattern illustrated by Fig. 2 are supplied to the track circuit of section W--X, and when the traffic conditions in advance are such 40 as to cause relay XRI to be released code impulses of direct current of the pattern illustrated by Fig. 3 are supplied to the track circuit of section W-X.

The track circuit for section W-X is provided 45 with two code following relays WCF and WTC Whose respective operating windings I8 and I Si are connected in parallel across the rails at the .end W of the section. The relay WTC is preferably of the direct current polar type charac- 50 terized by its polar armature remaining in the last position to which it was lmoved when the relay becomes deenergized. That is to say, contact members 2l! and 2l of relay WTC remain in the position to which they were last moved 55 when the operating winding I9 of the relay is deenergized. Relay WTC is so arranged that when winding I9 is energized by current of positive polarity its contact members 2B and 2l are moved to the right-hand position as viewed in 60 Fig. 1 to engage the respective contacts 2d and 25, and when winding I9 is energized by current of negative polarity the contact members 2li-and 2| are moved to the left-hand position as viewed in Fig. 1 to engage contacts 22 and 23, respec- 65 tively. Relay WTC is further so proportioned as to be effectively energized and operated in response to both the high and low voltage current impulses supplied to the track circuit of section W-X in the manner explained hereinbefore. 70 The relay WCF may be of the direct current polar type characterized by the fact that its contact members 26 and 21 are bia-sed'to engage respective left-hand contacts 28 and 29 when the relay is deenergized as well as when operating 75 winding I8 of the relay is energized by current of y age current impulses of positive polarity supplied to the track circuit but not by the low voltage current impulses of positive polarity.

Consequently, when traic conditions are such as to cause relay XRI to be picked up so that the current impulses supplied to the track circuit of section W-X are of the code pattern illustrated by Fig. 2, that is, a high voltage positive impulse and a low voltage negative impulse each operation cycle, the code following relay WTC is cperated to its right-hand position by each current impulse of positive polarity and to its lefthand position by each current impulse of negative polarity. The code following relay WCF is operated to its right-hand position by each current impulse of positive polarity and is oper-- ated back to its left-hand position by the biasing element of the relay when the current impulse of positive polarity ceases, the biasing element being aided, of course, by the energization of relay WCF by the low voltage current impulse of negative polarity. When traiic conditions are such as to cause relay XRI to be released so that the track circuit of section W-X is supplied with current impulses of the code pattern illustrated by Fig. 3, that is, a high voltage negative impulse and a low voltage positive impulse each operation cycle, the code following relay WTC is operated in step with the impulses as before, but the code following relay WCF is held inactive at its left-hand position.

I have found that when code following relay WTC is of the type and adjustment here proposed, it is operated to its two positions for substantially equal periods in response to the code patterns here proposed, and in addition the operation periods are practically of the same length regardless of changes in ballast resistance caused by wet or dry conditions with the result that practically uniform operation of the decoding apparatus to be shortly described controlled by the code following relay is assured.

The code following relays WCF and WTC are used to control two decoding relays WRI and WR3, while relay RI controls in turn a repeater relay WRZ. Relays WRI, WR2 and R3 are preferably of the direct current type, relay WRi being provided with a relatively long predetermined slow pick-up period, say, for example, 3 seconds; relay WR2 being provided with a slow release period of say, for example, 3 seconds, and preferably with a slow pick-up period also; and relay WR3 being provided with a slow release period suincient to span from one high voltage current impulse of the track circuit to the next.

Relays WRI, W'R2 and WR3 are here used to control the operation circuits of a wayside signal WS which governs tranic through the section W-X, and also to control the supply of code impulses of current to the track circuit for the section next in the rear of section W-X. The wayside signal WS may be any one of the standard three-position type of signals and is here shown as a color light signal having a green lamp 32, a yellow lamp 33 and a red lamp 34 for displaying clear, approach and stop signal indications, respectively. The relay WRI controls at its front contact Ila and back contact Ilia, the supply of current to the track circuit for the section next in the rear of sec-tion W-X in the same manner that relay XRI controls at its front contact I'I and back contact III the supply of current to the track circuit of section W-X.

It is believed that the circuits and the manner whereby code following relays WCF and WTC control the relays WRI, WRZ and WR3, and the control effected by these latter relays can best be understood by a description of the operation of the apparatus of the track circuit for section W-X. At the start it is to lbe observed that repeater relay WR2 is controlled over a simple circuit including back contact 35 of relay WRI and consequently relay WRZ is energized and picked up at the end of its slow pick-up period when relay WRI is released closing back contact 35, and relay WR2 is deenergized and released at the end of its slow release period when relay WRI is picked up opening back contact 35.

Assuming that relay XRI is picked up so that current impulses of the code pattern illustrated in Fig. 2 are supplied to the track circuit of section W--X and section W--X is unoccupied, code following relays WTC and WCE1 are both operated to the right-hand position by each high voltage current impulse of positive polarity, relay WTC is operated to its left-hand position by each low voltage impulse of current of negative polarity and relay WCF is operated to its left-hand position by its biasing element subsequent to each of such high voltage current impulses. Hence, relays WTC'and WCF are both operated at a rate corresponding to the code rate of the current impulses supplied to the track circuit.

When relay WTC is operated to its right-hand position closing contact ZIJ-24, direct current is supplied over either one of two alternative circuits to the top half portion of a primary winding 36 of a decoding transformer WDT. One of such circuits includes terminal B of any convenient source of -direct current such as a battery not shown, front contact 3'I of repeater relay WR2, wire 38, contact 23-24 of relay WTC, top half portion of primary winding 35 of transformer WDT and terminal C of the same source of current. The other alternative circuit extends from terminal B over back contact 39 of relay WRZ, front contact Iii) of relay WRI, wire 38, and thence as before traced. Each time relay WCT is operated to its left-hand position closing contact 2li-22, direct current is supplied to the lower half portion of primary winding 35 over the above traced alternative circuits, as will be apparent by an inspection of Fig. l. It is to be noted that a condenser 4I is preferably connected across the primary winding 3G to improve the operation. It follows that an electromotive force having a frequency corresponding to the rate at which relay WTC is operated is induced in the secondary winding 42 of transformer WDT.

The secondary winding i2 of transformer WDT is connected with relay WRI over a circuit having two alternative paths one of which can be traced from a mid terminal of secondary winding 42 over wire 43, winding of relay WRI, contact 2I-25 of relay WTC and to the lower outside terminal of secondary winding 42; and the other of which paths can be traced from the mid terminal over wire 3, winding of relay WRI, contact ill-23 of relay WIC, contact 26-28 of relay WCF and to the upper outside terminal of secondary winding 42. It is clear, therefore, that the electrornotive force induced in secondary winding 42 due to the operation of relay WTC is rectiiied and relay WRI is energized by the unidirectional current supplied thereto. Repeater relay WRZ is now deenergized and released because relay WRI is picked up opening back contact 35.

With code following relay WCF operated to periodically close contact 2I-3I, current impulses are supplied to relay WR3 over a simple circuit and that relay is effectively energized and picked up, relay WR3 remaining picked up from one impulse to the next by virtue of its slow release period.

With relays WRI and WR3 picked up and relay WR2 released a signal circuit is completed from terminal B over lamp 32, front contact 41 of relay WR3, back contact M of relay WR2, front contact F35 of relay WRE and to terminal C, and lamp 32 is illuminated so that signal WS displays a clear indication. It is to be noted that front contact I'Ia of relay WRI is now closed so that the current impulses supplied to the track circuit for the section next in the rear will be of the code pattern illustrated in Fig. 2.

Assuming next that relay XRI is released so that the code impulses supplied to the track circuit of section W--X are of the code pattern illustrated by Fig. 3 and section W-X is unoccupied, the code following relay WTC is operated the same as before but code following relay WCE remains inactive at its left-hand po-sition. Again, the operation of code following relay WTC causes unidirectional current to be supplied to relay WRI through the decoding transformer WDT so WR2 is released. Relay WR3 is now deenergized and released because code following relay WCF is inactive and held at its left-hand position.

With relay WRI picked up and both relays WRZ and WR3 released, a signal circuit is completed from terminal B over lamp 33, back contact 46 of relay W'R3, back contact 44 of relay WR2, front contact 45 of relay WRI and to terminal C, and lamp 33 is illuminated causing signal WS to display an approach indication. It is to be noted that front contact Via of relay WRI is still closed so that the track circuit forv the section next in the rear is still supplied with current impulses of the code pattern illustrated in Fig. 2.

Assuming next that a train occupies section W-X to shunt the track circuit so that code following relays WTC and WCF are inactive, relay 'WClE1 is held at its left-hand position by the biasing element of the relay and relay WTC is held at once or the other of its two positions. No current is now supplied to relay WRI and that relay is released with Ithe result that the repeater relay WR2 is energized and picked up at the end of its slow pick-up period. Relay WR3 is also released because relay WCF is inactive.

With relays WRI and WR3 released and repeater relay WRZ picked up, a signal circuit is completed from terminal B over lamp 35, back contact 35 of relay WRI and to terminal C', and lamp 34 is illuminated to cause signal WS to display a stop indication. Since relay WRI is released closing back contact Ia the current impulses supplied to the track circuit for the section next in the rear are of the code pattern illustrated by Rig. 3.

It is to be observed that when a train enters section W-X to shunt the track circuit, relay 35 g that relay WRI is picked up and repeater relay WRI is released almost immediately opening the circuit to the primary winding 36 of decoding transformer WDT, and opening the clear signal circuit and closing the stop signal circuit. With relay WRI released so that repeater relay WR2 is energized and picked up at the end of its slow pick-up period to close the other alternative cir- `cuit for supplying current to the primary winding 3b, it follows that as soon as current impulses again are supplied to code following relay WTC to operate that relay the decoding relay WR! is at once supplied with unidirectional current through the decoding transformer. However, if the train shunt is poor and one or two current impulses reach relay WTC strong enough to operate that relay, the relay WRI is not picked up unless a number of successive impulses suflicient to span the slow pick-up period provided for relay WR! flow past the train shunt to operate the code following relay WTC. Furthermore, should a sufficient number of current impulses ow past the train shunt so that the decoding relay WRI is picked up, neither the approach nor clear signal circuit is closed until the end of the slow release period of repeater relay WR2 and relay WR2 is released closing back contact M. It follows, therefore, that if the track circuit current impulses have a code rate of, say, 'l5 per minute, the relays WRI and WRZ can readily be adjusted so that five or six or even more successive current impulses are necessary to restore the apparatus and complete either the approach or clear signal circuit.

It should be observed that relay XRI which controls the supply of current to the track circuit of section W-X is itself controlled by the code following relays XCF and XTC of the track circuit next in advance of section W-X in the same manner that relay WR! is controlled by the code following relays WCF and WTC of the track circuit for section W-X. Consequently, when the section next in advance is unoccupied, relay XR! is picked up to cause current impulses of the code pattern of Fig. 2 to be supplied to the track circuit of section W-X and establish a clear signal indication for signal WS. When the section next in advance is occupied, relay XRI is released to cause current impulses of the code pattern of Fig. 3 to be supplied to the trtck circuit of section W-X and establish an approach signal indication for signal WS.

An advantage of apparatus embodying my invention is that the display of a proceed signal indication due to a loss of train shunt such as may ordinarily occur because of rusty rail surfaces or other operating conditions is avoided. Also, code following relays of the type here provided give a selective response to both the polarity and voltage code conditions of the track circuit current impulses. Also, as stated hereinbefore, such code following relays give substantially equal s0- called on and off operating periods.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

l. In combination, a track section, a source of direct current, a transformer having a secondary winding connected across the rails at one end of said section, a code transmitter including a contact member having a predetermined operation cycle to open and close a contact each said operation cycle, means including said contact to connect said direct current source with a primary winding of said transformer for supplying to the rails of said section a high Voltage impulse of current of a selected polarity each time said contact is opened and a low voltage impulse of current opposite in polarity to said selected polarity each time said contact is closed, a polar code following relay connected with the rails at the other end of said section operated when alternately energized by said current impulses of said selected polarity and said opposite polarity, another code following relay connected with the rails at said other end of the section biased to a first position and operated to a second position only when energized by said high Voltage current impulses of said selected polarity, and decoding relay means controlled jointly by said two code following relays.

2. In combination, a track section, a source of direct current, a transformer having a secondary winding connected across the rails at one end of said section, a code transmitter including a contact member having a predetermined operation cycle to open and close a contact each said operation cycle, means including said contact to connect said direct current source with a primary winding of said transformer for suplying to the rails of said section a high voltage impulse of current of a selected polarity each time said contact is opened and a low voltage impulse of current opposite in polarity to said selected polarity each, time said contact is closed, a first and a second code following relay connected with the rails at the other end of said section, said first relay operated to a first and a second position in step with said current impulses of said selected and opposite polarities, said second relay biased to a first position and operated to a second position only by said high voltage current impulse of said selected polarity, a slow pick-up relay, a slow release repeater relay controlled over a back contact of said slow pick-up relay, circuit means including a first position -and a second position contact of said first code following relay for supplying unidirectional current to said slow pickup relay, another slow release relay controlled over a second position contact of said second code following relay; and a signaling circuit including a front contact of said slow pick-up reiay, a back contact of said repeater relay and a front contact of said other relay.

3. In combination, a track section, a source of direct current, a transformer having a secondary winding connected across the rails at one end of said section, a code transmitter having a contact member operated at a predetermined rate, means including said contact member to connect said source of direct current with a primary winding of said transformer for supplying to the rails of said section impulses of current of a code rate corresponding to said predetermined operation rate of said contact member, a code following relay connected with the rails at the other end of said section respectively energized by each of said current impulses for operation of the relay at said code rate, a slow pick-up relay, a slow release repeater relay controlled over a back contact of said slow pick-up relay, decoding means controlled by said code following relay when operated for supplying current to said slow pick-up relay, and a signaling fcircuit including a front contact of said slow pickup relay in series with a back contact of said repeater relay for displaying a signal only when said code following relay is operated by a preselected number of successive impulses of current supplied to the rails.

4. In combination, a track section, a source of direct current, a transformer having a secondary winding connected across the rails at one end of said section, a code transmitter having a contact member operated at a predetermined rate, means including said contact member to connect said source of direct current with a primary winding of said transformer for supplying to the rails of said section impulses of current of a code rate corresponding to said predetermined operation rate of said contact member, a code following relay connected with the rails at the other end of said section effectively energized by each of said current impulses for operation of the relay at said code rate, a slow pick-up relay, a slow release repeater relay controlled over a back contact of said slow pick-up relay, decoding circuit means supplied with current either over a front Contact of said repeater relay or over a back contact of said repeater relay in series with a front contact of said slow pick-up relay, and said circuit means controlled by said code following relay when operated for supplying current impulses to said slow pick-up relay, a signal, and a circuit including a back contact of said repeater relay in series with a front contact of said slow pick-up relay to operate said signal only when said code following relay is operated by successive current impulses of a number predetermined by the interval formed by the pick-up period of said slow pickup relay plus the release period of said repeater relay.

5. In combination, a track section, a source of direct current, a transformer having a secondary winding connected across the rails at one end of said section, a code transmitter having a contact member operated at a predetermined rate, means including said contact member to connect said source of direct current with a primary winding of said transformer for supplying to the rails of said section impulses of current of a code rate corresponding to said predetermined operation rate of said contact member, a code following relay connected with the rails at the other end of said section effectively energized.

by each of said current impulses for operation of the relay at said code rate, a slow pick-up relay, a slow release repeater relay controlled over a back contact of said slow pick-up relay, a decoding transformer, a circuit Vincluding either a front contact of said repeater relay or a front contact of said slow pick-up relay and controlled by said code following relay when operated for supplying impulses of direct current to a primary winding of said decoding transformer to induce electromotive forces in the secondary winding of that transformer, another circuit for applying said electromotive forces to said slow pick-up relay to effectively energize that relay, a first signal circuit including a back contact of said slow pick-up relay, and a second signal circuit including a front contact of said slow pick-up relay in series with a back contact of said repeater relay whereby said first signal circuit is closed immediately after said two rails of said section are shunted and said second signal circuit is closed only after said code following relay has been operated by a predetermined number of successive impulses` of current.

6. In combination, a track section, a source of direct current, a code transmitter having a contact member operated at a predetermined rate, circuit means including said contact member and controlled by traffic conditions in advance of said section for supplying to the rails of the section from said current source current impulses of a first or a second code according to a first or a second trafiic condition in advance, said first code comprising alternate high voltage impulses of current of positive polarity and low voltage impulses of current of negative polarity, said second code comprising alternate high voltage impulses of current of negative polarity and low voltage impulses of current of positive polarity, a polar code following relay connected with the rails of said section effectively operated to a first and a second position in response to the polarity of said code impulses of current, another code following relay connected with the rails of said section biased to a rst position and effectively operated to a second position in response to said high voltage impulses of current of positive polarity only, a first decoding relay controlled over a first and a second position contact of said polar code following relay and a first position contact of said other code l following relay, a second decoding relay controlled over a second position contact of said other code following relay, and signal circuits selectively' controlled by said first and second decoding relays.

7. In combination, a track section, a source of direct current, a code transmitter having a contact member operated at a predetermined rate, circuit means including said contact member and controlled by traffic conditions in advance of said section for supplying to the rails of the section from said current source current impulses of a first or a second code according to a first or a second trafiic condition in advance, said first code comprising alternate high voltage impulses of current of positive polarity and low voltage impulses of current of negative polarity, said second code comprising alternate high voltage impulses of current of negative polarity and low voltage impulses of current of positive polarity, a polar code following relay connected with the rails of said section effectively operated to a first and a second position in response to the polarity of said code impulses of current, another code following relay connected with the rails of said section biased to a first position and effectively operated to a second position in response to said high voltage impulses of current of positive polarity only, a slow pick-up relay controlled over a first and a second position contact of said polar codefollowing relay, a slow release repeater relay controlled over aback contact of said slow pick-up relay, another slow release relay controlled over a second position contact of said other code following relay, la first signal circuit including a back contact of said slow pick-up relay; a second signal circuit including a front contact of said slow pick-up relay, a back contact of said repeater relay and a back contact of said other relay; and a third signal circuit including a front' contact of said slow pick-up relay, a back contact of said repeater relay and a front contact of said other relay.

' ANDREW J. SORENSEN. 

